The present invention relates to article holders or clamps for electroplating articles.
It is known in the art of electroplating to use frames on which are removably installed circuit boards or the like articles to be electroplated, for holding them while they are being submerged in large acid tanks or baths. The acid bath is one of several steps involved in the manufacture of a printed circuit board. The acid solution is usually either chloridric acid or sulfuric acid. The overhanging flames are made of an electrically conducting material sealed in a fluid-tight and electrically insulating material to substantially slow down the corrosive effects of the acidous vapors from the bath of acid, and are sealingly electrically connected to the articles to be plated. The frames are connected to a cathode element, or flight bar, and are subjected to an electrical current which is transmitted through the frame structure, the article and the liquid acid. An anode element is also submerged in the acid bath, spaced from the circuit board, for example of a distance of 6 to 10 inches. The potential difference between the article and the reducing agent anode element allows the metal composing the latter to migrate and attach itself onto the article. The metal composing the anode element can be for example copper, or any other suitable material combining a proper oxydo-reduction potential and suitable conductive characteristics.
An electroplating rack is shown in U.S. Pat. No. 4,176,039 issued in 1979 to J. C. Wismer. This electroplating rack includes clamps adapted to each hold one circuit board while it is submerged in an acid bath. The clamp holds the flat board on both sides, by means of a screw on a first side and a stopper on the other side. Both the screw and the stopper have electrically conducting cores destined to engage the board and connected to the flight bar, the cores being enveloped in sealing sleeves to help prevent corrosion thereof.
A first problem with the Wismer device is that the screw is likely to damage the board when it is rotated and pressed against the board. This is especially true when ultra-thin boards are to be installed on the clamp. Ultra-thin boards can be as thin as 0.002 inch. The damage to these board results mainly from the rotational movement and associated shearing effect of the screw, not from the transverse pressure applied on the board. In the case of the Wismer device, the resilient end seal provided at the screw tip around the electrically conducting core, is likely to enhance this problem due to the higher friction coefficient between the resilient seal material and the board. However, this seal is essential, or else the acid solution would have free access to the conducting core, the latter then being corroded at a high rate.
Another general problem with the Wismer device, is related to the maintenance of the electroplating rack. Although an end seal is provided at the screw tip, corrosion of the conducting core will still gradually occur at the screw tip. To remove the plating formed at the screw tip and resulting from this corrosion, the rack has to be submerged in a nitric acid bath or the like suitable solution which will allow the plating to be removed, which is a tedious and time-consuming operation. Alternately, the corroded parts, i.e. the screw tip and the stopper tip in the present case, have to be replaced, which is again time consuming, in addition to being expensive.
It is an object of the present invention to provide a clamp for holding articles to be electroplated, which has a replaceable connecting element which connects the article to the cathode flight bar.
It is a further object of the present invention to provide a connecting element which prevents friction movements of the clamp to occur against the article surface.
It is yet another object of the present invention that the connecting element allow the electric current to be transmitted on both sides of the article.
Therefore, in accordance with the objects of the invention, there is disclosed a spring clip for use as a connection member on an electroplating clamp, said spring clip being integrally formed of a folded, generally flat electrically conducting material and comprising a first and a second arm member and an arcuate foot member integrally linking said first and second arm members, said foot member having: a resilient elbow portion, allowing relative pivotal displacement of said first and second arm members between an opened condition, in which said first and second arm members spacedly register with one another and define a gap therebetween, and a closed condition, in which said first and second arm members are pivoted towards each other to at least reduce said gap therebetween, with said resilient elbow portion continuously biasing said first and second arm members towards said opened condition;xe2x80x94a first resilient lip, integrally formed between said elbow and said first arm member, said first lip protruding outwardly relative to said gap; andxe2x80x94a second resilient lip, integrally formed between said elbow and said second arm member, said second lip protruding inwardly toward said gap and toward said first lip.
Alternately, the invention more generally concerns a clamp for use on an electroplating rack of the type having an electrically conducting flight bar, said clamp comprising:xe2x80x94a main body made of an electrically insulating material;xe2x80x94an attachment member, for fixed attachment of said main body to the rack;xe2x80x94a conducting bridge member carried by said main body for electrical connection with the flight bar of said rack;xe2x80x94a spring clip carried by said main body and able to come into electrical contact with said bridge member, said spring clip being made of an electrically conducting material and being provided with first and second arms and an arcuate pivotable foot member linking said first and second arms, said pivotable foot member allowing relative pivotal displacement of said first and second arms between an opened condition in which said first and second arms spacedly register with one another so as to define a gap therebetween, and a closed condition, in which said first and second arms are pivoted towards each other to at least reduce said gap therebetween and in which said spring clip is in electrical contact with said bridge member;xe2x80x94a selectively operable pressure member carried by said main body and engageable with said spring clip so as to selectively pivot said first and second arms relative to each other from said opened condition towards said closed condition; andxe2x80x94a biasing member continuously biasing said first and second arm members toward said opened condition.
Preferably, said foot member of said spring clip is resilient and integrally links said first and second arms, said biasing member being said resilient foot member and continuously biasing said first and second arms towards said opened condition. Said spring clip could then be integrally formed of a folded, generally flat electrically conducting sheet, and wherein said foot member integrally linking said first and second arms comprises:xe2x80x94a resilient elbow portion allowing relative pivotal displacement of said first and second arms between said opened condition and said closed condition, with said resilient elbow portion continuously biasing said first and second arms towards said opened condition;xe2x80x94a first resilient lip, integrally formed between said elbow and said first arm, said first lip protruding outwardly relative to said gap; andxe2x80x94a second resilient lip, integrally formed between said elbow and said second arm, said second lip protruding inwardly toward said gap and toward said first lip.
Preferably, said pressure member is a screw threadingly engaging said clamp main body through a through-bore provided therein, said screw being able to gradually apply pressure on said spring clip second arm when said screw is rotated in a first direction to pivot said second arm towards said first arm and consequently pivot said first and second arms towards said closed condition, and said screw being able to gradually relieve the pressure on said spring clip second arm when said screw is rotated in a second direction opposite said first direction to allow said resilient foot member to bias said second arm away from said first arm and consequently pivot said first and second arms towards said opened condition. Said bridge member could then define a tip portion engageable with said spring clip at least when said first and second arms are in said closed condition, said clamp further comprising an insulating sleeve provided about said bridge member tip portion for sealing engagement against said spring clip about said bridge member tip portion at least when said first and second arms are in said closed condition. It is envisioned that said main body is generally U-shaped and defines a slot and a first lateral body portion for attachment to the rack, a second lateral body portion opposite said first body portion relative to said slot, and a web portion integrally linking said first and second lateral body portions, said spring clip being installed in said slot and being retained therein under said first and second arms being forced respectively against said first and second lateral body portions under the bias of said foot member, and said screw threadingly engaging a threaded through-bore made through said second lateral body portion, said screw having a tip portion engageable against said spring clip second arm. Said main body could also comprise a shoulder integrally formed in said slot, said spring clip first lip being capable of abutting against said shoulder to prevent accidental release of said spring clip from said slot. Preferably, said main body comprises a first block member and a second block member for attachment to on two opposide sides of the rack with said attachment member.
Alternately, the invention could also relate in still more general terms with an electroplating rack for electroplating an article in an acid bath, said rack comprising a cathode flight bar and a rack bar downwardly depending from said flight bar, said rack bar including an electrically conducting core electrically connected to said cathode flight bar and a fluid-tight, electrically insulating sheath enveloping said conducting core, said electroplating rack further comprising a clamp fixedly attached to said rack bar, said clamp comprising:xe2x80x94a main body made of an electrically insulating material;xe2x80x94an attachment member fixedly attaching said main body to said rack bar;xe2x80x94a conducting bridge member defining a core connection portion and a free tip portion, said bridge member being carried by said main body and being electrically connected with said rack bar conducting core at said core connection portion;xe2x80x94an electrically insulating and fluid-tight sleeve provided about said conducting bridge member and enveloping same except at said core connection portion and at said free tip portion, said sleeve comprising a seal portion near said bridge member free tip portion;xe2x80x94a spring clip carried by said main body and able to come into electrical contact with said bridge member free tip portion, said spring clip being made of an electrically conducting material and being provided with first and second arms and a pivotable foot member integrally linking said first and second arms, said pivotable foot member allowing relative pivotal displacement of said first and second arms between an opened condition in which said first and second arms are in spaced-apart register so as to define a gap therebetween, and a closed condition in which said first and second arms are pivoted towards each other to at least reduce said gap therebetween and in which said spring clip first arm is in electrical contact with said bridge member free tip portion, said seal portion of said sleeve engaging said spring clip about said bridge member free tip portion at least when said spring clip is in said closed condition so as to form a fluid-tight seal for said bride member free tip portion;xe2x80x94a biasing member continuously biasing said spring clip first and second arms towards said opened condition; andxe2x80x94a selectively operable pressure member carried by said main body and engageable with said spring clip so as to selectively pivot said first and second arms relative to each other from said opened condition towards said closed condition against the bias of said biasing member; wherein an article to be electroplated can be inserted into said gap between said first and second arms when said first and second arms are in said opened condition, said pressure member then being selectively operated to force said first and second arms into said closed condition for holding the article between said first and second arms, an electrical connection then existing sequentially through said flight bar, said conducting core, said bridge member, said spring clip and finally the article to be electroplated.
In this latter inventive concept, said foot member of said spring clip is preferably resilient and integrally links said first and second arms, said biasing member being said resilient foot member. Said spring clip could be integrally formed of a folded, generally flat electrically conducting sheet, and wherein said foot member integrally linking said first and second arms comprises:xe2x80x94a resilient elbow portion allowing relative pivotal displacement of said first and second arms between said opened condition and said closed condition, with said resilient elbow portion continuously biasing said first and second arms towards said opened condition;xe2x80x94a first resilient lip formed between said elbow and said first arm, said first lip protruding outwardly relative to said gap;xe2x80x94a second resilient lip formed between said elbow and said second arm, said second lip protruding inwardly toward said gap and toward said first lip.
Preferably, said pressure member is a screw threadingly engaging said clamp main body through a through-bore provided therein, said screw being able to gradually apply pressure on said spring clip second arm when it is rotated in a first direction to pivot said second arm towards said first arm and consequently pivot said first and second arms towards said closed condition, and said screw being able to gradually relieve the pressure on said spring clip second arm when it is rotated in a second direction opposite said first direction to allow said resilient foot member to bias said second arm away from said first arm and consequently pivot said first and second arms towards said opened condition.
Said main body could be generally U-shaped and define a slot and a first lateral body portion fixedly attached to said rack bar, a second lateral body portion opposite said first body portion relative to said slot, and a web portion integrally linking said first and second lateral body portions, said spring clip being installed in said slot and being retained therein under said first and second arms being forced respectively against said first and second lateral body portions under the bias of said foot member, and said through bore being made through said second lateral body portion. Said main body could also comprise a shoulder integrally formed in said slot, said spring clip first lip being capable of abutting against said shoulder to prevent accidental release of said spring clip from said slot. Said main body could also comprise a first block member and a second block member each engaging said rack bar on opposite sides thereof, and being attached to each other with said attachment member.
In an alternate embodiment of this latter inventive concept, there is provided an additional slot formed in said main body, with an additional spring clip being provided therein, and with an additional screw being engageable with said additional spring clip for releasably holding an additional article when said additional spring clip is in a closed condition, said clamp further comprising an additional bridge member electrically connected to said additional spring clip when said additional spring clip is in said closed condition, said rack comprising an additional rack bar having an additional conducting core enveloped in an additional insulating sheath, with said additional bridge member being electrically connected to said additional conducting core, said additional clamp being fixedly attached also to said additional rack bar with said attachment member, whereby the additional article can be carried by said clamp simultaneously with the first-named article.